WO2002018814A1 - Method and device for updating the reference position of an actuator on a clutch operating device - Google Patents

Abstract

The invention relates to a system for updating a reference position, stored in an electronic controller, for an actuator on a clutch operating device for a clutch contained in the drivetrain of a vehicle. Said system comprises an operating unit for operating the actuator, an incremental displacement measuring device for determining the distance covered by the actuator, a device for determining the achievement of a reference position for the actuator and storing the corresponding output signal from the incremental displacement measuring device as reference position and sensors for determining the status parameters of the drivetrain, whereby, upon a request for updating a reference position, the controller controls an updating process dependent upon the status parameters of the drivetrain.

Description

 METHOD AND DEVICE FOR UPDATING A REFERENCE POSITION OF AN ACTUATOR OF A CLUTCH ACTUATOR

The invention relates to a method and a device for updating a reference position of an actuator of a clutch actuating device stored in an electronic control device.

Automated clutches are being used not only because of the comfort you achieve, but also because of possible fuel savings in motor vehicles.

FIG. 4 shows an exemplary block diagram of a drive train of a motor vehicle equipped with an automated clutch. According to FIG. 4, the drive train of a motor vehicle contains an internal combustion engine 2, a clutch 4 and a transmission 6, from which a drive shaft 8 leads to drive wheels, not shown.

The transmission 6 is, for example, an automated manual transmission or a conical pulley belt transmission with continuously variable transmission ratio. An actuating device 9, which can be controlled from a selector device 10 by means of a selector lever 12 via a control device 14, serves to actuate or to switch the transmission 6. It goes without saying that the selection device can also be designed differently, for example as a classic shift lever (H-link) or as a lever with tapping positions (+, -) for shifting up and down.

The clutch 4 is, for example, a friction disk clutch with an actuating device 16, which is designed hydraulically, electrically (electromotively), electrohydraulically or in another way.

Sensors contained in the drive train, such as a pressure sensor 18 for detecting the intake pressure of the engine 2, a speed sensor 20 for detecting the speed n _{M of} the crankshaft of the engine, a sensor 22 for detecting the position of an accelerator pedal 24, and a sensor 26 for detecting the position of the Selector lever 12 and a further speed sensor 28 for detecting the speed of the drive shaft 2 are connected to the inputs of the control unit 14. In the control unit 14, which contains a microprocessor with associated memories 29, maps or programs are stored with which actuators, such as a load actuator 30 for adjusting the load of the motor 2, the actuating device 16 of the clutch 4 and the actuating device 9 of the transmission 6 are controlled become. The individual actuators can be constructed in such a way that their position is known directly in the control device 14, for example as stepper motors, or additional position transmitters can be provided.

The structure and function of the device described are known per se and are therefore not explained in detail. Depending on the driving request communicated via the accelerator pedal 24 and the desire for a driving program or a driving direction communicated via the selector lever 12, the load actuator 30, the actuating device 16 and the actuating device 9 are actuated in a mutually coordinated manner as a function of signals supplied by the sensors, so that there is comfortable driving.

For the actuation of the clutch 4, for example, a characteristic curve is stored in a memory of the control device 14, which defines a set position of the clutch 4 or an actuator of the clutch 4 set by the actuating device 16 as a function of a torque to be transmitted by the clutch 4 in each case , For reasons of control quality, clutch wear and energy consumption of the actuating device, the clutch torque that can be transmitted in each case should only be as large as is absolutely necessary. The required torque to be transmitted results from the driver's request or the position of the accelerator pedal 24 and, for example, the load of the internal combustion engine 2 detected by the sensor 18 and possibly further operating parameters, such as the speed of the engine 2 etc. The characteristic curve stored in the control unit 14, which indicates the desired path of an actuator moved by the actuating device 16 as a function of the calculated torque to be transmitted, has a decisive influence on comfortable starting and a comfortable handling of the switching operations. The characteristic changes over the course of the service life of the clutch and is updated or adjusted, for example, depending on wear in the presence of predetermined operating conditions, for example slipping at a predetermined engine torque, full engagement or disengagement of the clutch, etc.

FIG. 5 shows an example of the actuating device 16 in detail.

A piston 38, the shaft of which works in a cylinder 36 filled with hydraulic fluid

40 has an external toothing with an internal toothing of a gear

41 meshes, which in turn meshes with the external toothing of a pinion of an electric motor 42, which is controlled by the control unit 14 (FIG. 4). The electric motor can be a conventional switch motor that is controlled, for example, by means of a PWM signal. The cylinder 36 has a sniffer bore 44, which is connected via a line 45 to an expansion tank (not shown). A line 48 leads from the pressure chamber 46 of the cylinder, which leads to an actuating cylinder 50 of the clutch, in which an actuating piston 52 works, which is connected via its piston rod, for example, to the release lever 54 of the clutch which forms an actuator. The position A, which is generally referred to as the sniffer clutch zero position, is the position when it is passed over by the piston 38 according to FIG. 4 to the right in the pressure chamber 46, pressure for clutch actuation builds up.

To determine the position, an incremental position transmitter 32, known in its construction, is provided on the gear 41, for example, which counts the teeth of the gear 41 passing it and gives corresponding pulses to the control unit 14. The number of these impulses is a direct measure of the movement of the disengagement bels 54, at least as long as the piston 38 is to the right of the sniffer bore 44.

One problem that occurs in particular when using incremental position sensors or displacement sensors is that the current position of the component whose position is to be detected is lost. This current position is only available if the position transmitter's count corresponding to a reference position in the. Memory 29 of the control device 14 is stored and the number of increments or pulses by which the current position differs from the reference position is known. Both the reference position and the count by which the current position differs from the reference position can be lost due to a wide variety of influences. The loss of the then no longer known current position can lead to the actuating device moving an actuating component against a stop with full energy supply, which can lead directly to system failure, to a reduced service life or to other malfunctions.

The invention has for its object to provide a method or a system of the type described above, with which it is possible in a simple and safe manner to update a reference position so that the position of the actuator which is important in relation to the clutch actuation is known as reliably as possible.

The part of the object of the invention relating to the method is solved with the features of claim 1. With this method, a high degree of flexibility in updating is achieved, so that the position can be quickly and accurately detected again after the information about the position has been lost.

The method according to the invention is based in particular on the idea, for example, in situations in which the possible direction of actuation of the actuator for updating or aligning a reference position is not clear in the event of a slipping clutch, by means of further signals triggered by the driver, to determine the alignment or update direction or, if this is not possible, to maintain the current position.

The sub-claims 2 to 5 are directed to advantageous embodiments of the method according to the invention.

The claim 6 characterizes the basic structure of a system for solving the relevant part of the object of the invention.

The invention can be used for largely all types of automated clutch operations in which the position of an actuator must be known. The invention can be used particularly advantageously for clutch actuations in which an incremental displacement sensor is present.

The invention is explained below with reference to schematic drawings, for example and with further details.

They represent:

1 to 3: flow diagrams for explaining the invention,

4: the block diagram of a drive train of a vehicle with an automated clutch, and FIG. 5: an already explained example of a confirmation device.

A clutch normally has two reference positions of an actuator, namely a first reference position in which the clutch is fully closed and a second reference position in which the clutch is fully open. These positions are defined, for example, by stops or by the fact that the actuating force for adjusting the actuator, in the example of the release lever 54, suddenly changes. Information about the position related to a reference position or the absolute position of an actuator can be "lost" if the position X _n -ι preceding the counting of an increment ΔX is no longer correct, since the current position X _{n is in} each case from the last position and the Shift is determined by an increment.

Such a data loss or error typically occurs during a reset, whereby the system can be in any state, for example as a result of undervoltage (due to program runtime errors, in general, no resets may be triggered), through a modification or change in mechanical conditions, or through EMC problems.

Since a loss of the last position of the actuator cannot be ruled out, the system must be able to update or align the position information by moving to a reference position, comparing it with the stored values and correcting the stored values if necessary. This must be inconspicuous, without sacrificing comfort for the vehicle occupants, and if possible possible in every driving situation.

An update or adjustment must be carried out regularly when the system is started, when a reset occurs, or when implausible values are detected, for example when the clutch slips, even though the torque characteristic stored in the operating point does not allow any slippage or another, unforeseen operating point of the clutch is detected in the event of unexpected mechanical resistance or for regular checking of stored values. The route information is updated, for example, as follows: as soon as the request for an update is made, the drive unit, in the example of FIG. 5 the electric motor, is no longer controlled by the control unit 14 in a position-controlled or position-controlled manner, but rather is voltage-controlled. A reference position (clutch fully closed or clutch fully open) is identified, for example, by a sudden increase in current as a result of a sudden increase in force or by a sudden drop in current as a result of a sudden decrease in force.

The following table shows typical driving situations, each of which is associated with certain state parameters of the drive train, which are detected by the sensors shown in FIG. 4. The driving situation is determined independently of the clutch actuation or travel position, it being important to know the gear engaged in each case in accordance with the specified driving situation.

In the table, F state means a respective "software mode" of the clutch, that is to say a program according to which the clutch is controlled in each case. It goes without saying that different driving situations can occur within one mode, which results in the multiple answers in column 2. Among the individual F states means: normal driving

Creep (start)

tow-start

Disengaging to change gears

neutral gear

Sniff in neutral

Ignition "off" and switch off

"+" in columns 3 and 4 each means that an update is possible immediately, "0" means that an update is conditionally possible, and a "-" means that an update is impossible.

As can be seen from the table, states 3 to 6 permit an instantaneous update or an instant adjustment in such a way that the clutch is opened and the fully open reference position is updated in the process. The states 2, 3 and 4 and 8 allow an instantaneous update in the closing direction of the clutch.

A sniffing process is understood to mean a process in which the piston 38 is moved to the left beyond the sniffing bore 44 in accordance with FIG. 5 and is then moved to the right again until it passes over the sniffing bore. By sniffing, a volume compensation of the hydraulic system is possible. customary The clutch is completely closed, since a force can only be applied to the release lever 54 (FIG. 5) from the piston 38 when the piston 38 passes over the sniffer bore 44 from the left.

As can be seen from the table, in most driving situations an update can be carried out immediately by moving to one of the two reference positions.

The following are examples of update strategies:

1. Behavior when required to update and slip

When crawling and starting, the driver's request must be observed for safety reasons. Examples of security-critical situations are:

- When starting, the driver brakes because there are children on the road, but they do

The clutch is closed and the vehicle makes a "jump" forward.

When starting on the mountain, the driver accelerates, but the clutch opens and the vehicle rolls back.

In order to avoid these critical situations, there is no update or adjustment when the clutch is slipping, as long as no driver request can be identified that indicates the alignment direction. The driver's request can be indicated by operating the brake pedal (open clutch) or the accelerator pedal (close clutch).

1 shows a flow chart: If an update or an adjustment is required in step 60, it is first checked in step 62 whether the clutch is slipping. If this is the case, it is checked in step 64 whether the brake is actuated. If this is the case, the system decides that the clutch is opened in step 66, whereupon a position adjustment is carried out in step 72 by moving to the fully opened reference position. If it is determined in step 62 that there is no slippage, then if one of the relevant situations in the abovementioned table is present, the clutch is opened in step 66 and carried out in step 72. the position adjustment. If it is determined in step 64 that the brake is not actuated, then it is checked in step 68 how strongly the accelerator pedal is actuated. If this is actuated sufficiently, the clutch is closed in step 70, whereupon the closed reference position is approached in step 72. If it is determined in step 68 that the pedal reading is insufficient, the system returns to step 62.

It goes without saying that when the clutch is closed by means of a pure voltage control of the motor 42, the speed gradient of the vehicle engine 2 must be taken into account in order to avoid the engine stalling.

2. Coarse referencing of the position

The following applies to the clutch torque Mκu _PP during the slip phase _:

Mκu _PP = M _Mo t - chπ / dt, where M _Mo t is the motor torque that can be detected by the sensors, J is the moment of inertia of the motor and dtσ / dt is the temporal change in its angular velocity.

In control unit 14, the target position of the actuating member or the target clutch path is normally calculated from the target clutch torque. The torque characteristic is adjusted with adjustment parameters (coefficient of friction, gripping point) during the service life. If these parameters are known, the current position can be calculated from the current clutch torque. This position can be used as initialization value, on the basis of which the clutch is closed with the normal control strategy.

The relationships are shown in FIG. 2:

In step 80, an update or a comparison is requested. If the clutch is in a slipping state, the clutch torque is determined in step 82, as explained above, and the clutch position is determined from the stored torque characteristic. This clutch position can be used as a rough reference value for further control of the clutch actuation. For example, it can be determined in step 84 whether the slip has been eliminated. If this is the case, an update takes place in step 86, for example with voltage control of the electric motor 42. If this is not the case, the clutch can be operated further while maintaining the normal control strategy (step 88). If it is determined in step 80 that there is no slip, the system immediately goes to step 86. After step 88 is ended, the system jumps to step 84.

Regular updates in neutral

For the highest possible security of knowledge of the position, it is necessary to check it regularly. Therefore, an update can be routinely triggered in certain situations, this update being done in such a way that the driver does not notice it. A particularly suitable situation is when the vehicle is at a standstill with the engine running and neutral gear engaged. In this state, the clutch can be completely closed or opened so that its entire effective range can be traversed and both reference positions can be updated. After an update, the gripping point may have to be moved as well. Adaptations have to be postponed or adapted accordingly. 4. Regular updates while driving

Another option for updating is in state 8 (see table). The clutch is normally not fully closed, but only to such an extent that the transmittable clutch torque is slightly above the engine torque (torque tracking). This has the advantage that less time is required to open the clutch. To update, the clutch is operated in the closing direction. For routine volume compensation in the hydraulic transmission (sniffing), the clutch is also completely closed so that the closing position can be updated simultaneously with a sniffing process.

A strategy is also conceivable in which, with a certain certainty of the position knowledge, the clutch is brought as close as possible to its closed position and the closed position is then updated under voltage regulation. When the clutch is fully closed, both the update and the volume compensation (sniffing) can take place.

Rough update for a locked clutch

In the case of a system whose stop cannot be detected exactly reproducibly (for example when the clutch is closed), a rough update can take place in this direction. If a stop in this direction lies within the known inaccuracy, it is assumed that the current position is known to a certain extent and the old position is still considered to be valid. For safety, the energy supply to the motor can be limited in the vicinity of the end positions until an exact adjustment or an exact update can be carried out. If an update has not yet been carried out or the stop is outside the valid inaccuracy, the The position specified by the mentor is committed as the current position. The update will take place as soon as the possibilities have been added.

The flow chart according to FIG. 4 illustrates the relationships:

In step 90, an update in the direction of clutch closing is requested. A voltage-controlled closing takes place in step 92. In step 94, the reaching of a stop is recognized. In step 96 it is checked whether the position of the detected stop differs from the stored reference position by more than a threshold value. If this is the case, the position recognized in step 94 is stored in step 98 as new reference positions. In step 100, the rough adjustment is ended, but an exact adjustment as soon as possible is requested. If the deviation in step 96 is below the threshold value, the position is not updated in step 102, but an exact comparison is requested in step 101 as quickly as possible.

6. Update based on trust

If knowledge of the position is uncertain, an update takes place in the next possible situation, for example during normal driving towards the clutch or in the neutral position of the transmission towards the clutch. If there is uncertainty, the power with which the electric motor is controlled can be limited.

The claims submitted with the application are proposed without prejudice to achieve further patent protection. The applicant reserves the right to claim further combinations of features that were previously only disclosed in the description and / or drawings. Back-references used in subclaims indicate the further development of the subject matter of the main claim by the features of the respective subclaim; it is not to be understood as a waiver of the achievement of independent, objective protection for the combinations of features of the related subclaims.

Since the subjects of the subclaims can form their own and independent inventions with regard to the prior art on the priority date, the applicant reserves the right to make them the subject of independent claims or declarations of division. They can furthermore also contain independent inventions which have a design which is independent of the objects of the preceding subclaims.

The exemplary embodiments are not to be understood as a restriction of the invention. Rather, numerous changes and modifications are possible within the scope of the present disclosure, in particular such variants, elements and combinations and / or materials, for example by combining or modifying individuals in conjunction with those described in the general description and embodiments and the claims and features or elements or procedural steps contained in the drawings can be taken by the person skilled in the art with regard to the solution of the task and, through combinable features, lead to a new object or to new procedural steps or procedural step sequences, also insofar as they relate to manufacturing, testing and working processes.

Claims

claims 1. A method for updating a reference position, stored in an electronic control device, of an actuator of a clutch actuating device of a clutch contained in the drive train of a vehicle with one of the Control unit-controlled actuating unit for actuating the actuator, in which method the actuator is operated to update the reference position, the reaching of the reference position is recognized by a parameter changing in a predetermined manner, and a value corresponding to the current reference position reached is stored as an updated reference position in response to an update request, state parameters of the drive train in which the clutch is located are determined and the update takes place as a function of the state parameters. 2. The method according to claim 1, wherein a distance measurement of the actuation of the actuator takes place incrementally. 3. The method of claim 1 or 2, wherein a first reference position corresponds to the closed and a second reference position of the opened clutch and when the clutch slips, a reference position is only approached depending on the presence of predetermined, defined intentions of an operator corresponding situation parameters. 4. The method according to any one of claims 1 to 3, wherein a target position of the actuator is determined from the torque currently transmitted by the clutch and a torque characteristic stored in the control device and is used as the instantaneous actual position for a further clutch actuation. 5. The method according to any one of claims 1 to 4, wherein updates are carried out with the vehicle stationary, the transmission in neutral and the engine running. 6. The method according to any one of claims 1 to 5, wherein in the case of imprecise recognizability of a reference position, this reference position is approached and an update takes place only if the recognized reference position differs from the previously stored one by more than a predetermined threshold. 7. An apparatus for updating a reference position of an actuator of a clutch actuating device of a clutch contained in the drive train of a vehicle stored in an electronic control device, comprising an actuating unit controlled by the control device for actuating the actuator, an incrementally working displacement measuring device for detecting the distance covered by the actuator Means for detecting the reaching of a reference position of the actuator and storing the associated output signal of the incremental displacement measuring device as a reference position and sensors for detecting status parameters of the drive train, the control device controlling an update depending on the status parameters of the drive train in response to an update request for a reference position.